The state of Massachusetts has said it will appeal against a federal court ruling upholding Microsoft's controversial anti-trust deal with the US government.

Left to its own devices, Microsoft will continue to engage in predatory practices

Tom Reilly, Massachusetts attorney general

The appeal, if successful, could revive attempts by Microsoft's opponents to break the firm's dominance of the software market through legal sanctions.

Massachusetts is one of nine US states that refused to go along with a settlement last year which ended a federal government inquiry into alleged market abuse by the software giant.

The nine 'rebel' states argued that the original settlement let Microsoft off too lightly, and went back to court to press for tougher penalties.

Last stand

But US District Judge Colleen Kollar-Kotelly rejected their arguments earlier this month in a ruling which endorsed the original anti-trust deal.

Seven of the other eight rebel states said on Friday they would not challenge the decision, with the remaining state - West Virginia - due to decide by Monday.

Monday is the deadline for state authorities to decide whether to contest Ms Kollar Kotelly's ruling.

Massachusetts state officials said they would if necessary act alone in an effort to prevent possible future competitive abuses by Mircosoft.

"We are prepared to go our own way," said Massachusetts Attorney General Tom Reilly.

"Left to its own devices ... Microsoft will contine to engage in predatory practices and eliminate any real chance for consumer choice or business innovation."

Market dominance

The original anti-trust probe came in response to complaints that Microsoft had designed its Windows operating system - used on 80% of the world's personal computers - in such a way that it was difficult to run non-Microsoft products alongside it.

Microsoft was found guilty of anti-competitive behaviour, and, under the terms of the final settlement, was ordered to make technical information available to competitors so that they could design software that would run smoothly with Windows.

But the settlement stopped short of breaking Microsoft up into two separate companies, a measure that many of its opponents had called for.